The visual world contains more information than the brain can process. Fortunately, we have some ability to influence which sources of information receive processing priority through the mechanism of selective attention, and this ability is critical for daily life. Attention involves coordination across the brain at a global level to contol the balance of processing resources in functionally-specialized brain areas operating at a local level. To date, however, laboratory techniques for investigating the neural bases of attention, such as human scalp EEG and single-unit recordings in primates, have been sensitive to only one of these two levels of operation at a time. The goal of this research project is to combine these two methods in a single comprehensive investigation to characterize how these two levels of brain function, the global and the local, interact during control of selective attention. We hav developed a carefully titrated research strategy that will achieve this overarching goal through three systematic and specific aims. We will begin by establishing baseline measures of the links between correlated variability in small populations of neurons and EEG signals measured at the scalp, both in the spontaneous brain state as well as during basic visual perception. We will then add a layer of complexity by introducing an endogenous selective attention task, enabling us to expand our scope beyond low-level perception to higher-level cognitive processes. Finally, with an eye for potential applications of the knowledge gained from the preceding two aims, we will monitor attention signals with a 'closed-loop' system. This will enable us to monitor the animals' natural attentional fluctuations in order to present stimuli in a contextually optimal fashion. Such a 'brain-state-contingent' system would have clear advantages across a wide range of applications. Since this is a training award, another major goal of this project is the training of Dr. Adam C. Snyder, a promising postdoctoral fellow, in the techniques required for single-unit electrophysiology in non-human primates, as well as the professional practices that will be needed throughout what will undoubtedly be his long and productive career as an independent scientist. At the end of this project, Dr. Snyder will have received first-rate trainin in the practices of primate electrophysiology, which will complement his established and proven expertise in human EEG methods, strengthening his foundation as an innovative and successful neuroscientist. From a scientific perspective, we will have developed a model of attention control that spans local and global levels of brain function. This advancement will not only benefit attention research itself, but will provide a framework for future investigations of other brain processes that similarly operate across a range of spatial scales. An understanding of the functioning of attention in health individuals is essential to guide potential therapeutic interventions in disorders involving deficits in attention, including autism, schizophrenia and attention deficit disorder.